Abstract:

Freeze-thawing has an important effect on physicochemical properties of soil, the migration, transformation and the environmental effects of heavy metal in soils. The effects of freeze-thawing on absorption and desorption characteristics of Pb and Cd in black soil and brown soil were studied by laboratory simulation. The results showed that the absorption ability of Pb and Cd was stronger in black soil than that in brown soil. Freeze-thawing decreased absorption ability of Pb and Cd in the soils, resulting from the change of physicochemical properties of soils under the condition of freeze-thawing. The desorption quantity and rate of Pb and Cd in the soils increased with the increasing adsorption quantity of Pb and Cd. Freeze-thawing enhanced desorption of Pb and Cd in the two soils. However, the desorption ability of Pb and Cd in black soilwere weaker than that in brown soil in the same freeze-thawing condition. The reason is that freeze-thawing made absorption quantity of Pb and Cd in soils increasing was related with the decline of desorption solution pH. Freeze-thawing decreased retention ability of Pb and Cd in soils, consequently increasing ecological risk.

Key words: freeze-thawing, black soil, brown soil, heavy metals, adsorption/desorption